POS0316 SURVIVIN REGULATES T CELL RESPONSES THROUGH DEPOSITION OF HISTONE H3 MARKS AND MODULATES RESPONSE TO TREATMENT WITH JAK-INHIBITORS
Authors: K. M. Andersson, V. Chandrasekaran, M. Erlandsson, E. Malmhäll-Bah, S. Töyrä Silfverswärd, R. Pullerits, M. I. Bokarewa
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Multiple genetic polymorphisms are associated with high risk for rheumatoid arthritis (RA) [1]. The importance of epigenetic processes has been postulated, but precise molecular mechanisms behind these associations remain largely unexplored. Survivin is an important player in RA, which has been recently shown essential for IFNg signaling in CD4 T lymphocytes acting in partnership with IRF1 [2]. <h3>Objectives</h3> We study how survivin-dependent epigenetic deposition of histone H3 tails in RA risk loci affects function of CD4<sup>+</sup> T cells and response to JAK inhibition. <h3>Methods</h3> Chromatin of CD4<sup>+</sup> cells (n=12) was immunoprecipitated with antibodies to histone H3K27ac, H3K4me3, and survivin, and sequenced (ChIP-seq, Illumina). Parallel ChIP-seq and RNA-seq was done in CD4<sup>+</sup> cells treated with survivin inhibitor YM155. Peaks with change &gt;30% in deposition of H3K27ac and/or H3K4me3 upon YM155-treatment were annotated to the genomic regulatory elements (RE) via GeneHancer database. Single nucleotide polymorphism (SNP) related to RA risk were identified within those RE. CD4<sup>+</sup> T cell transcriptomics by RNA-seq was done in 24 random RA patients and in 59 RA patients treated with MTX (n=18), TNFi (n=10), JAKi (n=24) and having no DMARDs (n=7). The genes differentially expressed (DEG, nominal p&lt;0.05) in BIRC5<sup>hi</sup> and JAKi-treated CD4<sup>+</sup> cells were identified by DESeq2 (R-studio, Bioconductor). <h3>Results</h3> Deposition of 15% (1705/11152) of H3K4me3 and 17% (1943/11530) of H3K27ac peaks changed &gt;30% upon survivin-inhibition. Approximately 50% of these peaks overlapped with survivin peaks. The change in H3K4me3 peaks was significantly larger if the peak colocalized with survivin peak. These peaks were located within 228 RE, 28 of these RE contained 52 RA risk SNPs. Among others, changeable peaks were accumulated within ICOS/CTLA4/CD28 locus and contained 7 SNPs. Majority of genes connected to the SNP-containing RE (110/153 genes) were transcriptionally different in BIRC5<sup>hi</sup>CD4<sup>+</sup>T cells and participated in the regulation of immune system (GO:0002682, FDR=4.3e-4), regulation of IL2 production (GO:0032663, FDR=0.019), TNF mediated signaling (GO:0033209, FDR=5.4e-3). These SNP-RE connected genes formed three independent clusters 1) TCR receptor co-stimulators (CD40, ICOS, CTLA4, CD28, CD244, TRAF6 and TBX21, SLAMF1, TNFRSF9), 2) connected to the LCK interacting transmembrane adaptor 1 (LIME1, SLC2A4RG, ZGPAT, GMEB2, TNFRSF6B, RTEL1) and 3) heat-shock proteins (HSPD1, HSP90AB1, HDAC7, KPNB1). The clusters were functionally connected to survivin partners IRF1 and SMAD3. Notably, transcription of CD28, ICOS, and SLAMF1 functionally connected to IRF1, and CHERP, HDAC7, PRPF6 and SRSF10 functionally connected to SMAD3 were significantly changed (all, nominal p&lt;0.05) in CD4+ cells upon survivin inhibition by YM155. Since survivin mediates IFNg-dependent processes [2], we analyzed transcription of 110 SNP-RE connected DEG in CD4<sup>+</sup> cells of JAKi-treated RA patients. We found that DEG in the IRF1 and SMAD3 clusters were inversely affected by JAKi, e.g., IRF1-related CD28, ICOS, and SLAMF1 upregulated after survivin inhibition were suppressed by JAKi, while SMAD3 related CHERP, PRPF6 down-regulated by survivin inhibition were upregulated in CD4+ cells of JAKi-treated patients. Effect of JAKi in the IRF1-related genes was executed only in BIRC5<sup>lo</sup>CD4<sup>+</sup> cells and remained unchanged in BIRC5<sup>hi</sup>CD4<sup>+</sup> cells. <h3>Conclusion</h3> This study shows that survivin contributes to deposition of histone H3K27ac and H3K4me4 marks in proximity of RA-risk genes and control immune system regulators in CD4 T cells. JAK-inhibitors operate downstream of survivin and high levels of survivin may impede JAKi-treatment. <h3>References</h3> [1]Okada Y et al. Ann Rheum Dis 2019, 78(4):446-453 [2]Erlandsson MC et al. iScience 2022, 25(12):105526 <h3>Acknowledgements</h3> We thank the research nurses Anneli Lund and Marie-Louise Andersson at Rheumatology Clinic, Sahlgrenska University Hospital, Gothenburg, for blood sampling. We thank all RA patients who participated. <h3>Disclosure of Interests</h3> None Declared.